These studies will use electron microscopy to examine the synaptic relationships of neurons within the visual cortex (areas 17 and 18) of the macaque monkey. Normal cortical tissue and Golgi impregnations will be examined by electron microscopy to identify the type and sites of synaptic contact made by identified interneurons of particular laminae. The maturation of different synapse populations will be examined both quantitatively and qualitatively and the effects of visual deprivation upon synapse maturation assessed. This work will provide an essential correlate to ongoing light microscopic and physiological investigation of visual cortex structure and function. Information obtained from these studies should provide a better understanding of the mode of function of the primate visual cortex and give a baseline for understanding the nature and causes of defects in the visual system arising during early formation of neural connections.